I may be part of the unpopular opinion but leveling to 30 was not bad whatsoever. I just got to 30 about two weeks ago, and before that the grind didn't bother me at all. I was more focused on leveling my mastery scores with various champions that I liked. I didn't even save or start buying any runes until I hit level 30, and I did fine against players with full rune pages.
The only REAL problem with being a new player are smurf accounts. Other than that, all other players dealt with the same shitty tutorial and shitty recommended items. At the same time, you can't give new players everything. You can't just automatically recommend them the best build path for their character, as it is constantly changing and it's something they need to learn on their own. A player who wants to be better should know to look up guides. Watch streamers. Watch YouTube videos. Do your studying. It's a hard game to adjust to. It takes a long time to know EVERYTHING. Ultimately, I don't think the tutorial is THAT bad. It leaves a lot to be desired, but I don't feel like I was incredibly lost as a newbie.
The Internet is a powerful thing. If you're dissatisfied with the information the game gives you, look up more.
As far as experience gains, I personally didn't even realize wins gave you more exp. I didn't usually look at the numbers and leveling happened pretty fast anyways. I feel like a lot of people have the natural "play to win" competitive attitude regardless. Even if wins gave the same exp as losses, a lot of people would still be focused on winning. It's in our nature. There has to be SOME reward for winning. It makes sense to me at least that when you show you're a decent player (by winning a lot of games) you progress to level 30 faster. If you're a bad player and lose an obnoxious amount, the game merely holds you back because you have more to learn. When you learn what you're doing wrong, you'll fix it and be on your path to winning.
TLDR; The new user experience is not as bad as people make it out to be. New players have extra sources they can take advantage of (Google, YouTube, twitch). Runes don't make THAT much of a difference. And more exp for winning encourages people who are getting the hang of the game, and holds back those who have more to learn. It's there for a reason.